Nitrification inhibitors in agroecosystems: what we know, what we don’t and why it matters

Purpose Nitrogen (N) is a key macronutrient applied in cropping system to enhance productivity; however, less than 50% of applied N is utilised by crops. Substantial N losses occur through nitrification and subsequent NO 3 − leaching, denitrification or NH 3 volatilisation, resulting in economic losses and environmental pollution. This review examines the roles of chemical nitrification inhibitors (NIs) and biological NIs (BNIs) in improving N-use efficiency and mitigating soil- and environment-related N losses. Materials and methods This review synthesizes evidence from laboratory, pot and field studies assessing the impact of NIs and BNIs on soil N transformation processes with a focus on rhizosphere interactions involving microbial activity, plant nutrient uptake, heavy metal bioavailability and interactions with residual agrochemicals across diverse soil and climatic conditions. Results and Discussion NIs delay the oxidation of ammonium to nitrate, thereby improving crop N uptake; however, concerns remain regarding their persistence and non-target effects on soil microbial communities. BNIs offer a promising nature-based alternative by regulating nitrification within the rhizosphere, although their limited diffusion into bulk soil may reduce effectiveness. Both NIs and BNIs influence N cycling, microbial dynamics and trace metal mobilization, with outcomes dependent on soil properties, management practices and environmental conditions. Conclusion NIs are an important tool for enhancing N-use efficiency and mitigating environmental N losses. Future research should focus on mechanistic understanding, non-target impacts and climatic influences to support their sustainable integration into N management strategies.